Function repo_key 

async fn repo_key(cwd: &Path, budget: Duration) -> PathBuf

The repository a checkout belongs to, as the fetch gate’s key: git’s common dir, canonicalised.

Keyed on the common dir rather than the scan cwd because linked worktrees share refs/remotes/*. Two seats in <repo> and <repo>/.claude/worktrees/x - this project’s normal layout - contend for one ref lock, so a gate keyed per cwd would let both fetch at once and misattribute the loser’s refusal. A path git cannot answer for falls back to the cwd: a separate gate cannot deadlock, it only fails to serialise.